Human-machine interfaces often utilize press detectors that can receive touch input for interaction with digital content, machine controls, etc. Press detectors can be configured for use with many types of applications and surfaces including, for example, car dashboard controls, touch/gesture input for portable computing devices, outdoor or harsh environment control buttons, etc. Such press detectors enable tactile human-machine interaction in a natural and preferred way.
Piezoelectric impact detectors formed from polymeric materials such as polyvinylidene fluoride (PVDF) offer cost effective and high performance detection of momentary forces, such as the push of a button or a surface, the closure of a door or latch, or the passing of a person or vehicle. These thermoplastic fluoropolymer materials can be made very thin and are typically resistant to solvents, acids, and bases. PVDF is a material that works very well in the construction of surfaces or thin sensor modules for touch and press detection. However, many piezoelectric materials such as PVDF have the disadvantage that they also respond to temperature changes, often with pyroelectric coefficients that rival their piezo coefficients. Thus, touch sensors made with materials having a large pyroelectric coefficient can produce a false signal due to a temperature change, such as for example, in a vehicle when it moves from an air-conditioned environment into extreme weather, or between shadows and hot sun. A need exists for press detectors having a reduced thermal response.